Background and Purpose:
Several published studies have described the MR imaging findings which occur with variable frequency in cases of Spinal Dural Arteriovenous Fistula (SDAVF). While hyperintensity within the center of the cord on T2-weighted images has been reported as the most consistently observed finding, 1 it is not specific. Saraf-Lavi and colleagues2 showed that the observation of flow voids on T2-weighted fast-spin-echo images, and serpentine enhancement on postcontrast T1-weighted images, for a length exceeding three vertebral levels were each strongly associated with the presence of dural AVF, yet these findings are not always evident, or may be spurious and due to CSF pulsation artifacts. A recent study3 suggested that peripheral spinal cord hypointensity on T2-weighted images may be a reliable sign of venous hypertensive myelopathy and in particular of SDAVF. The purpose of this study is to evaluate the accuracy of this sign in predicting SDAVF.

Methods:
Gradient-echo axial images of 21 subjects with surgically proven DAVF (diagnosed with x-ray digital subtraction angiography, DSA) and 9 control subjects, who had normal DSA, were retrospectively reviewed by 2 experienced neuroradiologists blinded to the final diagnosis. The control group included subjects with abnormal cord signal intensity. The reviewers were asked to indicate “yes” or “no” in response to the question, “Is peripheral spinal cord hypointensity present?” Sensitivity, specificity, positive and negative predictive values were calculated. The level of agreement between the reviewers was also calculated.

Results:
Peripheral spinal cord hypointensity was observed in 9 of 20 patients with proven SDAVF, and in 2 of 9 control subjects. Sensitivity, specificity, and accuracy, as well as positive and negative predictive values, for each reviewer are presented in Table 1.

Kappa value was 0.71 representing good agreement between the reviewers beyond chance.

Table 1

Sensitivity

Specifity

PPV

NPV

Accuracy

Reviewer1

45%

78%

82%

39%

55%

Reviewer2

30%

67%

67

30%

41%

Conclusion:
The finding on T2-weighted images of peripheral spinal cord hypointensity in association with SDAVF has been attributed to slow flow of blood containing deoxyhemoglobin within a distended spinal cord capillary and venous system.3 Quencer4 has questioned whether the finding represent a real pathologic alteration or a visual phenomenon produced by the sandwiching of the peripheral cord between two hyperintense regions, the frequently observed hyperintensity of the central cord in SDAVF and the hyperintensity of the CSF surrounding the cord. Whatever the basis for the finding, our results indicate that the majority of patients with SDAVF are unlikely to exhibit peripheral cord hypointensity – as evidenced by the very low sensitivity in our study. Interestingly, peripheral cord hypointensity was observed in the control group. We conclude that peripheral cord hyperintensity is not a highly reliable sign of SDAVF. Based on the results for PPV, though, we suggest that when the sign is present, a more meticulous search should be instituted for other signs that are more strongly associated with the presence of SDAVF.